\name{sigmoid}
\alias{sigmoid}
\alias{dsigmoid}
\alias{d2sigmoid}
\title{sigmoid functions}
\description{
Some sigmoid functions. See R sources for their definition
}
\usage{
sigmoid(x)
dsigmoid(x)
}
\arguments{
\item{x}{ numeric vector }
}
\author{ J. L. Aznarte }
\keyword{ ts }
